This project is based upon the utilization of non-invasive canopy-spirometer-computer-system for the prolonged measurement of spirometry and gas exchange in normal adult subjects and patients with various surgical diseases. The spirometry signals are obtained without touching the faces or the upper airway of the individual and computer processing on-line yields a series of graphs which provide a detailed summary of the study for prompt review. An on-going study is being conducted to define the breathing pattern as a function of age and sex, when the artifacts of conventional measuring equipment are not preset. This data is to serve for comparison with measurements of acutely ill surgical patients. With special attention to tidal volume, frequency, minute ventilation, inspiratory and expiratory time, mean inspiratory flow rate and mean expiratory dwell time. Preliminary studies have established the feasibility of this system for measuring the response to ventilatory stimulation using inspired CO2 or measured amounts of supine exercise. Such studies are being adapted for use with surgical patients, where the simultaneous response in gas exchange and ventilatory pattern may characterize the patients physiologic and metabolic reserve in a new way. Our long-range goal is to provide earlier recognition of the loss of breathing reserve and a more sensitive means of following the results of ventilatory therapy.